French physician Renť LaŽnnec invented the stethoscope in 1816, when he was unable to feel a patient's heartbeat through his hand or by pressing his ear against the chest due to the patient's "great degree of fatness". His first stethoscope was a hollow wooden tube, one end pressed against the patient's chest and the other end held to the doctor's ear. Decades after his death the stethoscope was improved with two further innovations -- rubber tubing, and binaural earpieces.

The stethoscope, now seen as a doctor's fundamental tool, allowed LaŽnnec to diagnose diseases earlier and more accurately than had previously been possible. He conducted landmark studies of lung, liver, and skin diseases, and he was one of the first doctors to perform autopsies to learn more about the evidence and processes of disease. He coined the medical terms cirrhosis (describing the growth of small tissues that cause liver degeneration) and melanoma (the darkened surface indicative of skin cancer). He is the namesake of "LaŽnnec's thrombus," a blood clot of the heart, and "LaŽnnec's cirrhosis", a specific form of progressive liver disease. He wrote the first detailed medical descriptions of bronchiectasis, emphysema, pleuritis, and pneumonia, and showed that lesions called tubercles, visible in any of the body's organs, are a definitive symptom of tuberculosis. Ironically, this finding allowed LaŽnnec to diagnose his own advancing tuberculosis, which killed him at the age of 45.